The committee of Roman Catholic bishops charged with drafting a policy statement on nuclear warfare for the church in this country has concluded that there are virtually no circumstances under which the use of nuclear weapons is morally acceptable.

First use of nuclear weapons, no matter how restricted the scale, and use of nuclear weapons against population centers or other predominantly civilian targets are categorically ruled out by the position paper, according to sources familiar with the document.

Use of nuclear weapons can be morally justified only after similar weapons have been used against the United States or its allies, and then only against exclusively military targets in circumstances that would not endanger civilians, the document states. The statement expresses what one knowledgeable figure described as "grave skepticism" that those conditions could ever be met.

The document, reflecting 18 months of study by a five-member committee of bishops headed by Archbishop Joseph L. Bernardin of Cincinnati, will be distributed Monday to the nation's 280 bishops, who are cloistered in an unprecedented 10-day retreat in Collegeville, Minn.

While the document will not be debated there, it is being distributed now, a church spokesman said, so that the prelates can consult and think about it in preparation for final action in November.

The policy statement that evolves out of the debate and is adopted by the bishops this fall will become the official moral teaching of the church in this country. The nation's 50 million Catholics will not necessarily be bound to agree with it, but they will be obliged to consider it seriously in forming their own consciences.

The nuclear arms race has been a growing concern for many prelates. More than half the church's bishops have endorsed a nuclear weapons freeze. Whereas the Catholic peace movement, as recently as the Vietnam war years, was largely scorned by the hierarchy, a sizeable number of bishops are now looked to as heroes and leaders of that movement.

The substance of the Bernardin committee's conclusions leaked out when a member, Auxiliary Bishop Thomas J. Gumbleton of Detroit, summarized the main points during a seminar of the Catholic Theological Society of America, meeting last week in New York. According to a knowledgeable source here, who asked not to be identified, the paper makes six main points on the morality of nuclear weapons:

No use on civilian targets, ever, under any circumstances.

* No first strike, on however restricted a scale.

* Any threatened use must be governed by points 1 and 2.

* If nuclear weapons may ever be used, it is only in retaliation for a nuclear attack, and then "only in an extremely limited, discriminating manner against military targets," the source said, adding, "we don't really believe these conditions can be met."

* Possession of nuclear weapons as a deterrent. is morally acceptable only if there is a commitment to the first four rules.

* The morality of any use or even possession of nuclear weaponry is contingent on the government's willingness to engage "seriously" and "energetically" in negotiations for arms reductions.

The statement reportedly is very emphatic on the need for the U.S. government to take the initiative in negotiations leading to arms reduction.

In developing its position statement, the Bernardin committee, which was carefully chosen to include hawks and doves of the hierarchy, took testimony from scores of experts ranging from representatives of the antinuclear Ground Zero movement to Defense Secretary Caspar Weinberger. The goal was to produce a nuclear age version of the church's traditional guidelines on a just war.